Overhaul Entire Front Suspension

In continuing my quest to restore the M5 mechanically, I sought to tighten up the front suspension. Rather than diagnose each part, I decided to replace every component. FCP had a kit, but I wanted to upgrade the upper control arm bushings to the Moosehead Engineering spherical bushings, which could be ordered already pressed into Lemforder upper control arms. Thus, I ordered all of the remaining parts of the kit à la carte. I chose Lemforder for every component, except for the steering center link, which was only available from Meyle. The lower control arms are aluminum.

I read up a lot about remove the control arm ball joints and the days of hammering people had gone through to get them to release. I bought a “front-end” tool kit with various pullers and ball joint separators. With the proper tools and my impact wrench, I found it pretty easy to get the key attachment points undone. I removed the entire assembly as a unit from the car and then used the ball joint separator to free the left and right tie rod levers, which were the only parts being reused.

The tie rod levers had some surface rust and would have looked a little out of place connected to all the new shiny parts, so I decided to paint them with POR 15 for aesthetic reasons only. Once they were dry, I was ready to assemble all the components together before installing them on the car. Once I was under the car, I started cleaning adjacent parts and just couldn’t stop. I found it a lot easier to remove the sway bars and some heat shields than try to clean them in place.

When it was all back together, I was very pleased. I had never worked on my suspension before, aside from doing the rear subframe. I immediately took it to our local tire shop for an alignment. Afterwards, the entire front end was so solid and the handling was crisp, as I imagine it was when the car was new. This was one of the biggest and most gratifying jobs I had ever tackled.

Replace Rear Subframe Bushings and Pitman Arms

Even though I fixed the driveline shudder, there was still a very pronounced “clunk” coming from the rear end. This is a common problem and easily diagnosed as failed rear subframe bushings. I read a lot about what a PITA job this is, not only to get the old bushings out (101 ways, including a sawzall), but also to get the new bushings in.

I ordered new Lemforder subframe bushings and Pitman arms (dogbones) as well as new pins and nuts. I also had to borrow a special tool, which is used to remove and install the subframe bushings. The first step was to put my new bushings on ice to make them easier to install.

It didn’t take long during the removal step to realize the both old bushings were destroyed, with the inner part completely separated with the outer part, thus rendering them completely ineffective. I still needed to use the BMW Sir Tools 3026, which is no longer available, to remove the old bushings, which are pressed into the subframe and likely bonded to it after all these years. With the proper tool, they pressed right out.

The new Pitman arms were a lot easier to remove and replace. I was also very happy to have my new Milwaukee M18 impact wrench, which made quick work of spinning off the old nuts. The new ones sure looked a lot nicer than the old ones, which were very clearly worn.

After removing the subframe bushings from the freezer and spraying them down with water and a drop of dish soap, they actually pressed in pretty easily. I kept tightening the nut on the tool to try to get the bottom of the bushing to press all the way into the subframe. Despite not getting quite there, I ended up crushing the thrust bearing, which was actually kind of scary as the bearings flew out in many directions (eye protection!). The took came with a replacement bearing, so I was able to also complete the other side. What I realized was that the bushing is slightly taller than the subframe, so when it gets pressed into subframe all the way, it is then getting compressed within the tool versus going in any further. I didn’t try it, but it seems that using the cup that is used for removing the bushing instead of the flat plat designed to accept only the bushing “ears,” would allow the bushing to be pressed further into the subframe and then let the bottom be pressed in to the ridge of the bushing.

In the end, I had to source some real thrust bearings that matched the size and specifications of the original ones, as I didn’t want the owner of the tool to be stuck with a hobbled tool.

This repair completely eliminated the rear-end “clunk” and tightened up the handling considerably.

Replace Rear Differential Mount

From day 1, the M5 had a strange vibration in the driveline. I tried to diagnose it and had several possible root causes. There was some also possibly unrelated clunking coming from the rear. Before I knew what the subframe bushings entailed, the rear differential mount was discussed a lot. By its positioning and function, it seemed to be a likely candidate for replacement.

Rarely is the consensus on the internet, but one thing that was suggested often was to use the part from the Euro M535i (33171129786), which was more robust and less expensive than the OEM M5 part. I sourced a Lemforder part from FCP Euro. It was a pretty easy procedure, but unfortunately did not eliminate the clunking.

Around this time, my speedometer was intermittent. I found that the speedometer cable was rubbing on the differential output and shorting out. I taped it up and the problem was fixed. I was thankful it wasn’t anything more serious.